docs: def zoom(self, value):
          """Zoom level."""
          if isinstance(value, (int, float)):
              value = (value, value)
          assert len(value) == 2
          self._zoom = np.clip(value, self._zmin, self._zmax)
  
          # Constrain bounding box.
          self._constrain_pan()
          self._constrain_zoom()
  
          self.update()